Recent studies of Alzheimer's disease with position emission tomography (PET) have shown focal reductions in glucose metabolism that thus far have no post-mortem morphometric or biochemical correlates. The purpose of this project is to evaluate the significance of these changes by determining whether they closely reflect progression of symptoms. It is hypothesized that the regional differences in glucose utilization seen in the early stages of dementia will be obscured as the disease worsens, and that the pattern of abnormal glucose metabolism will be useful in predicting the course of intellectual decline. To test these ideas local glucose metabolism will be estimated by PET using fluorodeoxyglucose annually for five years in a group of patients with clinically diagnosed Alzheimer's disease and age-matched controls. In the first year scans will be done both with and without diazepam sedation so that the effects of diazepam and anxiety can be assessed. Subsequent scans will all be done with the patient sedated so that patients at all stages of their illness can be studied despite behavioral disturbances. Annual psychometric and neurological examinations performed in parallel with PET will permit comparison of metabolic and symptomatic changes and the study of specific patterns of glucose metabolism. These findings can also be compared to the changes seen in normal aging subjects. Post-mortem confirmation of the clinical diagnosis will be sought in all cases. Achievement of the above goals will (1) validate a sedation technique so that PET can be used even when full cooperation is not possible; (2) assess the usefulness of PET in studying Alzheimer's disease; (3) and assist in the interpretation of post-mortem biochemical and pathological studies.